The present invention relates to an automatic travelling apparatus capable of identifying a permissible travel path for the purpose of permitting a vehicle to automatically run on a road.
Recently, there has been developed an automatic travelling apparatus which is capable of identifying a permissible travel path, setting a target course thereon and steering a vehicle to run along the target course.
The automatic travelling apparatus disclosed in Japanese laid open patent publication No. 199610-88 continuously generates an image of an area ahead of a vehicle and in the vehicle's running direction using an image pick-up device attached to the vehicle. The apparatus samples the image thus generated and extracts therefrom continuous line segments such as road edges. The apparatus then determines a permissible travel path ahead of the vehicle based on the extracted continuous line segments and sets a target course in the determined permissible travel path. Next, the apparatus estimates a steering correction necessary to allow the vehicle to follow the target course based on the currently detected running condition of the vehicle and, based on the steering correction, steers the vehicle to follow the target course.
Because the above-mentioned automatic travelling apparatus performs the steering control of the vehicle at repeated sampling intervals, the steering control will be more accurate as the sampling period i.e., steering control cycle, is made shorter.
However, where the processing of generated image data is performed by a microcomputer or like means, the processing may take a rather long time because an image of an area ahead of the vehicle may be complicated and may include a large amount of information to be processed. Thus, it is often difficult to reduce the control cycle time of an image processing system.
The time required for processing each image and for determining a permissible travel path is fairly long in comparison with the processing time required for steering the vehicle to follow the target course set in the permissible travel path. For example, where image processing may take 500 milliseconds to complete, the processing time required for steering control may take only 10 milliseconds.
If the image processing time is extended, the vehicle may travel enough to produce a deviation from its actual position with respect to the determined permissible travel path, causing a considerable decrease in accuracy of the steering control. It will be noted that, as the running speed of the vehicle increases, the amount of deviation will also increase.